With the rapid progress of plastics industry, current plastics throughput of the world has far beyond hundred million tons. On the basis of statistics, worldwide synthetic resin throughput in 1999 is 156,700,000 tons. The use thereof has reached every section of national economy as well as every field of daily life. Among them, plastic packaging material and articles account for about 30 percent, approximately 46,000,000 tons. Only for china, consumption of synthetic resin in 1999 is 18,660,000 tons. The articles for plastic packaging are 5 million tons. That is to say, the consumption of plastic articles for packaging is huge.
The rapid increase of plastic consumption and advance of environmental sense of the people make that the research of degradable plastic is increasingly concerned. Recently some patents (for example Chinese patent application No:95191396) reports that new type polymer (such as microorganism polyester, aliphatic polyester, poly(lactic acid) and the like) of structure unit readily affected by light and microorganism is made by use of synthetic method. When this new type polymer is discarded after use, it can be degraded by utilizing the direct effect of illumination or microorganism. The degradability of degradable plastics made by this method is very good, but difficultly applied in great amount in market owes to synthesis difficulty thereof, and high cost.
Other patents (for example Chinese patent application No:98106850.2 and 98101407.0) report a “photodegradable and photodisintegrable” material. They adopt the process that photosensitizer, or the blend of photosensitizer with mineral powder of calcium carbonate, talc and the like is added to plastic raw material. Due to the fact that these materials are only subjected to photodisintegration, the degradation thereof is the change of from chunk to nub, satisfactory results are hardly obtained.
Still other patents (for example Chinese patent application No:95121178 and 99100726.3) report that a “biodegradable starch resin” is made by adding as the inducement of biodegradation, starch to plastic raw material. As is well known, starch can be utilized by microorganism, but the macromolecular of above-mentioned general plastics still hardly degradable. Finally only some pore is leaved in the surface of these “degraded plastic articles”, it is difficult to attain degradation in true sense. Additionally, granule of starch is often large, influences mechanical property, and it is difficult to make article of high strength and in thin thickness. At the same time, starch is readily absorbing water, however in the processing, even in the case of very low water content, bubble is also readily produced in the plastic articles. Starch is readily scorched at a high temperature, however the processing temperature of plastic is often high. For example, some companies adopt “biodegradable starch resin” mixed with high density polyethylene, which is blown to manufacture shopping bags, and due to the fact that starch is readily scorched, it is difficult to continuously make film.
All these impose numerous inconvenience to the processing of plastics. That is to say, the prior art can not realize truly degradation of general plastics themselves which are hugely used in the market, eliminate and reduce “white pollution”, realize friendliness to environment.